A conveyor such as an escalator and a moving platform includes a plurality of steps each having guide rollers on front and rear sides. These steps are supported by the guide rollers that are engaged with step guide rails provided in a structure, and the steps are circulated between an entrance port and an exit port, while horizontal postures of the steps are maintained. The steps are generally connected to each other by means of a step chain. By driving the step chain, all the steps are configured to be synchronically moved without generating a gap therebetween.
The step chain is driven by a driving mechanism which is generally of a type for driving chain ends by sprockets. In general, such a driving mechanism is disposed near an entrance port or an exit port. However, in a conveyor in which a travel distance of the steps are long, there is a possibility that a sufficient driving force cannot be transmitted by only the driving mechanism disposed on the chain end, because of an increased load applied to the step chain. Thus, in a conveyor in which a travel distance of the steps are long, it has been proposed to arrange a plurality of driving mechanisms to give a driving force at intermediate positions (a position other than an end at which the chain turns by changing directions) of a long chain (see, Patent Documents 2 and 3, for example).
The driving mechanism for giving a driving force at an intermediate position of a chain in a conveyor generally includes a motor as a driving force source, a reduction gear for amplifying a driving force by a factor of 10 or more, and a chain driving force transmitting mechanism for transmitting a driving force to a linearly extended step chain. When a sprocket is used as the chain driving force transmitting mechanism, a meshing rate is decreased because the linear chain is not wound round the sprocket. Thus, there is used a chain driving force transmitting mechanism shown in FIGS. 16(a) and 16(b).
As shown in FIGS. 16(a) and 16(b), in a driving force transmitting mechanism 100, a step chain for connecting steps 101 is formed as a tooth chain 102 of a long link length, and the tooth chain 102 is driven by rotating circulating chain 104 provided with pin rollers 103.
[Patent Document 1] JP2004-224567A
[Patent Document 2] JP47-19989U
[Patent Document 3] JP47-10873A
However, when such a tooth chain 102 of a long link length is used as a step chain, a speed irregularity may easily occur, as compared with a general step chain, at an end of the conveyor where the tooth chain 102 turns to change directions. Thus, it is difficult to invert the steps 101 with the use of a circular sprocket which is uniformly rotated. Thus, when the tooth chain 102 is used as a step chain, a guide rail of a pseudo-circular shape has to be used to invert the tooth chain 102. As a result, a driving mechanism using an inexpensive and general sprocket is difficult to be used as a driving mechanism for driving a step chain.
As a driving mechanism for giving a driving force at an intermediate position of a conveyor apparatus, a driving mechanism of a type that is capable of driving a generally used step chain is preferred.
However, a general step chain is of a short link length, so that a sufficient meshing angle cannot be guaranteed to drive circulating chain in circulation. Thus, it is necessary to dispose a mechanism for preventing a step chain from floating.
In a conveyor apparatus in which a conveyor chain of relatively a long link is used as a step chain, contrivances in shape is necessary, e.g., a link length of circulating chain is increased to be equal to or more than the link length of the step chain, in order to make deeper a meshing angle of the circulating chain relative to the step chain.
However, in a driving mechanism disposed at an intermediate position of a conveyor apparatus, when circulating chain whose link length is equal to or larger than that of a conveyor chain is driven in circulation by a general sprocket, the number of teeth of the sprocket is not enough. Thus, pulsing motions occur in the circulating chains and the step chain to thereby impair a ride quality of a step.
In addition, even when a link of the circulating chain is elongated to allow contrivances in shape, since a concrete shape for making deeper a meshing has not been disclosed heretofore, such a shape must be additionally invented.
The present invention has been made in view of the above disadvantages. The object of the present invention is to provide a conveyor apparatus including a driving mechanism for giving a driving force at an intermediate position of the conveyor apparatus, the conveyor apparatus being capable of giving a driving force to a general step chain while achieving a sufficient meshing angle. In particular, the object of the present invention is to provide a conveyor apparatus free of pulsing motion in circulating chain to provide a comfortable ride quality on steps, even when a conveyor chain of relatively a long link is used as a step chain and the circulating chain of a long link to be engageable with the step chain is driven by a general sprocket.